Comments

Answers

0

The pop up might be executed by a custom action. You should write a log file while uninstalling the product and
as soon as the message box pops up you open up the log file then you will see the action which shows the pop up
at the bottom of the log file.

As soon as you know the name of the action just give it a never to meet condition in the Install Execute Sequence table
like "...AND 1=2", save this as a transform and use it for your uninstallation.